In the operation of bulk material conveyors, a belt scraper assembly is provided for removing adhering material from the conveyor belt and depositing it into a discharge area. In the absence of a cleaning device, or as a result of a poorly functioning belt scraper, carry-over will be accumulated beneath the conveyor belt. In addition to consituting a nuisance, a large amount of valuable product will be deposited beneath the conveyor and may build up sufficiently to interfere with operation of the conveyor. For example, a volume of spillage material 1/16" (1.6 mm) deep and 1" (25 mm) wide will produce approximately 21/2 cubic feet (0.075 cubic meters) of carry-over per 100 feet per minute (0.48 meters per second) of belt speed each hour. At a conveyor speed of 500 feet per minute (2.5 meters per second), this small stream produces approximately 10 tonnes of carry-over spillage every eight hours, based on a density of 100 lbs per cubic foot (1500 kg/cubic meter).
Consequently, there is considerable interest in improving the operation and efficiency of conveyor belt cleaning devices, which generally include one or more scraper blades disposed in a plane transverse to the conveyor belt and are urged toward the belt so as to cause engagement of an edge of the blade with the belt surface. The belt cleaning device is hampered constantly by obstructions such as mechanical fasteners moving at high speeds, which are often driven by hundreds of horsepower. Moreover, if the belt reverses, the reverse movement of the conveyor belt can drive the blades into the belt and cause tearing of the conveyor belt or damage to the scraper. This problem occurs frequently on inclined conveyors where the hold back allows the belt to reverse even a few inches before locking. It also occurs when a traveling tripper is moved forward when the belt is stopped.